1. Field of the Invention
The present invention relates to a tube for a heat exchanger and a method of manufacturing a tube, in which a fluid for a heat exchange flows. The heat exchanger can be suitably used as a radiator for a vehicle, for example.
2. Description of the Related Art
In a vehicle having an internal combustion engine, a heat exchanger such as a radiator for cooling engine coolant of the internal combustion engine is generally provided. In the heat exchanger, a plurality of tubes in which the coolant flows are arranged so that heat exchange is performed between air passing through the heat exchanger and the coolant flowing in the tubes, thereby cooling the coolant.
For example, JP-A-10-47875 proposes a tube for the heat exchanger, in which a projection J20 is formed by bending at a center portion of a metal plate in a width direction of the metal plate, as shown in FIG. 5. In the tube shown in FIG. 5, opposite two inner surfaces of the projection J20 are brazed, and two end portions of the metal plate are brazed to the outside surfaces of the projection J20 in a thickness direction of the projection J20 so as to form an inner column portion J200.
In the tube shown in FIG. 5, the inner column portion J200 is provided to partition an inner space of the tube into two fluid passages, thereby improving pressure resistance in the tube. However, when the tube is bonded to a core plate of a tank, a heating process is performed in a state where the tube is inserted into a tube insertion hole of the core plate. In the heating process, a melted brazing material of the core plate flows into the inner column portion J200 from the portions X shown in FIG. 5 by a capillary action. The brazing material flowing into the inner column portion J200 flows toward a center portion of a core portion of the heat exchanger, and are used for bonding the tube and a fin of the core portion. In this case, a brazing material for bonding the tube and the core plate of the tank may become insufficient, thereby causing a brazing insufficient problem.
In a tube for a heat exchanger described in JP-A-2003-202196, as shown in FIG. 6, one end portion J11 of a metal plate is bent approximately in a U shape to form an inner column portion J200. A first brazing portion J2a is formed so that the inner column portion J200 is brazed to an inner surface of the tube at the first brazing portion J2a. Furthermore, the other end portion J12 of the metal plate is bent to be bonded to the inner column portion J200 at a second brazing portion J2b. In this case, because one position of the brazing portions J2a, J2b of the metal plate is exposed to an exterior of the tube, the brazing material entering into the inner column portion in the tube can be reduced. Accordingly, it can restrict a brazing material for brazing the tube and the core plate from being insufficient.
In the tube shown in FIG. 6, a length L10 of the second brazing portion J2b is smaller than a length L20 of the inner column portion J200. Therefore, a part of the inner column portion J200 has the sectional area of the single metal plate, thereby reducing a pressure resistance of the tube. In this case, a center portion of the tube may be deformed during a heating process.